Gear shifting transmissions of motor vehicles are usually shifted or controlled using an operating device disposed within reach of the driver. Actuating elements such as shift levers or selector levers are used customarily for this purpose, and are disposed between the front seats of the motor vehicle, for example.
In regards to modern operating devices, a particular requirement for the driver is to be provided with a realistic feel for the actuation of the transmission, for reasons of safety and ergonomics. It is therefore necessary that the driver be provided with visual feedback as well as clear haptic or tactile feedback regarding the current gear state or operating state of the transmission.
In regards to shift-by-wire-controlled gear shifting transmissions in particular—which also include most current automatic transmissions—it is required, for ergonomic and safety reasons, that the driver be provided with visual and haptic signals that certain gear states or shift operations are not permitted at a particular moment in the form of blocking the corresponding actuating positions of the selector lever.
When gear shifting transmissions are actuated electrically or using shift-by-wire, which is becoming increasingly more common, the selector lever in the passenger compartment and the motor vehicle transmission in the engine compartment are not mechanically coupled. Instead, in the case of “shift-by-wire” transmissions, the shift commands are transmitted from the operating device to the motor vehicle transmission using electrical or electronic signals, and the shift commands are then usually implemented at the transmission using electrohydraulics.
In shift-by-wire-controlled gear shifting transmissions, however, the absence of a mechanical connection between the transmission actuator system and the selector lever leads to the result that the transmission state or any shift locks that have been engaged in the transmission can no longer react directly to the state of the selector lever. Since certain gear positions are not noticeably blocked at the selector lever, the driver is unable to easily recognize that some lever positions, gear selection positions, or transmission states may not be permitted in the current drive state and therefore cannot be selected.
Depending on the state of the gear shifting transmission to be operated, and depending on other state factors of the motor vehicle—ignition switched on, engine running, vehicle speed, etc.—in order to implement haptic feedback in shift-by-wire-controlled transmissions, it is therefore generally necessary to limit the range of operation of the selector lever in an actuator-controlled manner depending on the transmission state. In this manner, when the driver reaches for the selector lever, he can recognize in a haptically noticeable manner—even with a shift-by-wire transmission—that his shift request is not permitted and is therefore blocked, for example due to the current operating state or driving condition of the motor vehicle, or due to the current operating state of the gear shifting transmission.
The interrelationships described herein are also of particular significance in regards to monostable operating devices for shift-by-wire transmissions. Monostable selector levers are frequently used with by-wire-controlled transmissions since complex actuator systems can be eliminated that are otherwise used to reposition the selector lever if an automatic state change happens to occur in the transmission, for example if the parking lock is automatically engaged (Auto-P).
In the case of a monostable operating device, the selector lever has one stable (center) position and usually a plurality of non-stable positions in various directions starting from the stable (center) position. Depending on the transmission state, however, usually only a few of all of the mechanical selector lever positions that are available are even feasible for the particular actual shift operation. Other selector lever positions that are indeed mechanically possible for the selector lever to attain, however, cannot or should not—depending on the transmission state—trigger a meaningful shift operation, and must therefore be blocked using actuators to provide the driver with a consistent haptic sensation at the selector lever and with reliable feedback about any shift locks.
For example, if the transmission is in the “parking lock” state, a monostable selector lever must be prevented from being moved further forward—relative to the direction of travel—even if the selector lever could indeed be moved out of its center position and moved freely, at first, in the forward direction. Instead, an appropriate actuator system must ensure that the selector lever in this example can only be moved backward relative to the direction of travel.
As is apparent in US 2006/0016287 A1 or DE 10 2005 033 510 A1, for example, attempts have been made to correct this problem by equipping selector levers of shift-by-wire-controlled gear shifting transmissions with multiple-action actuators, and with appropriate lever elements or transmission elements to selectively block impermissible shift commands. These actuators and the lever elements or transmission elements thusly controlled are shifted depending on the vehicle state or transmission state to thereby limit the original overall range of motion of the selector lever corresponding to the current driving condition or transmission state, or to block the selector lever entirely in certain cases.
However, if a plurality of different selector lever positions in different combinations must be blocked using actuators, or if the range of motion of the selector lever must be positioned variably within an angular range, then, according to the prior art, a complex locking mimicry is often required for this purpose. This has unwanted consequences, due to the complexity and increased costs associated therewith. A conventional locking actuator system of this type can also encounter problems in terms of the construction space available in the region of the operating device. Furthermore, the locking devices known from the prior art tend to produce considerable noise levels and due to the relatively slow shift times of the locking devices can result in certain situations in the problem of one of the selector lever locks being overshot and, associated therewith, the problem of undefined operating states of the operating device occurring.